Window assemblies typically include a frame and a pair of sashes mounted for reciprocal vertical or horizontal sliding movement, one relative to the other, on guide rails in a frame jamb. These assemblies can also include sash locks, security locks or locking assemblies which are either spring-loaded or manually activated to secure the window sashes or panels in a locked, closed position.
Many of today's modern windows include vinyl, vinyl-clad aluminum extrusion or vinyl-clad wooden sashes containing vent stops. Vent stops are typically mounted on the inside surface of the upper sash and are manually activated to extend from a flush position to an extended position over the top rail of the lower sash. This permits the windows to move relative to one another to provide a vent opening through the window, but limits the size of the vent opening. Vent stops can reduce burglaries since they can be positioned to permit a relative opening which is too small for the torso of a human being. They also minimize the risk of small children falling through open windows, since they can be positioned on one of the sashes to create a vented opening which is even too small for children.
Most vent stops contain an internal metal spring which creates a biasing action so that the stop can be selectively placed in an extended open position. Since the metal spring is an additional cost item, requires additional assembly time and is subject to corrosion, a need presently exists for a better biasing mechanism. In order to be accepted in the window trade, such a mechanism must be capable of a minimum of 4,000 cycles of use prior to failure.